Mesleki İngilizce - Technical English

II • Notes: Prof. Dr. Nizamettin AYDIN – In the slides, • texts enclosed by curly parenthesis, {…}, are examples. • texts enclosed by square parenthesis, […], are [email protected] explanations related to examples.

http://www.yildiz.edu.tr/~naydin

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Networks Networks

• Learning Objectives • Keywords – to acquire basic vocabulary related to network – Connection concepts • In networking, a connection refers to pieces of related information that are transferred through a network – to become familiar with different technologies – Packet – to understanding, the limits, capabilities, and • A packet is the most basic unit that is transferred over a benefits of specific network hardware network. • Sub-areas covered • When communicating over a network, packets are the envelopes that carry your data from one end point to the other – networks – Network Interface – • A network interface can refer to any kind of software interface to networking hardware

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Networks Networks

• Keywords • Keywords – LAN • stands for "local area network". – Bandwidth • refers to a network or a portion of a network that is not • the amount of data that can be carried from one point to publicly accessible to the greater internet another in a given time period – WAN • stands for "wide area network". – Topology • means a network that is much more extensive than a LAN. • The physical layout of a network – Protocol – • a set of rules and standards that basically define a language that devices can use to communicate. • the study of encryption and decryption. • There are a great number of protocols in use extensively in networking, and they are often implemented in different layers.

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1 Networks Networks-Introduction

• Reading text • Comparing a data network to a living organism, • Pre-reading questions – the hardware provides the skeleton or basic infrastructure upon which the nervous system is built. – What is a protocol? • Similarly, a few hundred meters of cable running – Which device forwards packets between networks through the walls of a laboratory is necessary by processing the information included in the packet? – but insufficient to constitute a network. – What is called the physical or logical arrangement • Rather, the data pulsing through cables or other of network? media in a coordinated fashion define a network. – Which system spans states, countries, or the whole world?

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Networks-Introduction Networks-Introduction

• This coordination is provided by that • The Internet was a natural successor to the cold – connect workstations and shared computer war projects in the 1950s and early 1960s with the networks – amplify, route, filter, block, and translate data. • The modern Internet was the unintended • An informatics researcher should have a basic outcome of two early complex systems: understanding of the limits, capabilities, and – the ARPANET (Advanced Research Project benefits of specific network hardware, Agency Network) – to be able to converse intelligently with hardware – the SAGE system (semiautomatic ground vendors environment), – to direct the management of an information services • developed for the in the early 1950s and 1960s, provider. respectively.

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Networks-Introduction Networks-Introduction

• SAGE was the national air defense system • The communications network component of the SAGE system was comprehensive and extended beyond the comprised of border of the U.S. and included ships and aircraft. – an elaborate, ad hoc network of incompatible • It was primarily a military system, – with a civil defense link as its only tie with civilian command and control , communications system. – early warning systems, • In the 1950s and 1960s, federally funded researchers at – weather centers, academic institutions explored ways to manage the growing store of digital data amid the increasingly – air traffic control centers, complex network of computers and networks. – ships, • One development was hypertext, – a cross-referencing scheme, – planes, • where a word in one document is linked to a word in the same or a – weapons systems. different document.

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2 Networks-Introduction Networks-Introduction

• Around the time the ARPANET was born, a • In addition to applications for the military, a variety of number of academic researchers began commercial, hypertext-based document management systems were spun out of academia and commercial experimenting with computer-based systems that laboratories, used hypertext. – such as the Owl Guide hypertext program from the University of – For example, in the early 1970s, a team at Carnegie- Kent, England, and Mellon University developed ZOG, – the Notecards system from Xerox PARC in California. • a hypertext-based system that was eventually installed on a • Both of these systems were essentially stand-alone U.S. aircraft carrier. equivalents of a modern Web browser, • ZOG was a reference application that provided the – but based on proprietary document formats with content limited to what could be stored on a hard drive or local area network crew with online documentation that was richly (LAN). cross-linked to improve speed and efficiency of • In this circuitous way, out of the quest for national security locating data relevant to operating shipboard through an indestructible communications network, equipment. – the modern Internet was born.

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Networks-Example Networks-Example

• Microarray Laboratory Network • The computers in a typical microarray laboratory present a mixture of – data formats, – operating systems, – processing capabilities. • The network in this example (a wired and local area network) supports – the microarray laboratory processes, • from experimental design and array fabrication to expression analysis and publishing of results.

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Networks Networks

• A should be examined from the perspective of: • Network Taxonomy – Geographical scope – Underlying model or models used to implement the network – transmission technology – Bandwidth or speed – Physical layout or topology – Protocol or standards used to define how are handled by the network – Ownership or funding source involved in network development – Hardware, including • cables, wires, and other media used to provide the information conduit from one device to the next – Content carried by the network

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3 Networks Networks

• There are multiple networking Technologies: • Geographical Scope – Personal Area Network (PAN) – Local Area Network (LAN) • The geographical extent of a network is – Metropolitan Area Network (MAN) significant because it affects – Wide Area Network (WAN) – bandwidth, – (SAN) – Enterprise private network (EPN) – security, – Virtual private network (VPN) – response time, – Global Area Network (GAN) – the type of possible. – Wireless Local Area Network (WLAN) • For example, it is only because of the high-speed – Controller Area Network (CAN) Internet backbone that real-time teleconferencing and – Internet Area Network (IAN) model sharing are possible on a worldwide basis.

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Networks Networks

• Informatics R&D incorporates network resources on worldwide (WAN), • PAN institution-wide (MAN), and laboratory-wide (LAN and PAN) levels. – personal area network • a used for communication among computer devices, – including , personal digital assistants, … • limited to the immediate proximity of the user, or about a 10-meter radius, • If PAN is constructed using wireless technology, – known as wireless personal area network (WPAN)

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Networks Networks

• PAN • LAN – local area network • a network that is restricted to smaller physical areas – extend to about 100-meters from a central server, or a single floor in a typical research building. • e.g. a local office, school, or house. • Approximately all current LANs whether wired or wireless are based on . • Data transfer speeds can extend to – 10.0 Mbps (Ethernet network) – 1.0 Gbps (Gigabit ethernet) • Coaxial cable and CAT 5 cables are normally used for connection.

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4 Networks Networks

• LAN • MAN – Metropolitan Area Network • take over where LANs leave off, – covering entire buildings and extending tens of kilometers. • typically implemented with digital subscriber line (DSL), cable , and fixed wireless technologies. • Several LANs are often connected to make a MAN. – When this configuration is used for a college campus, it is referred to as a campus area network (CAN).

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Networks Networks

• MAN • WAN – Wide Area Network • connects computers together over large physical distances, – such as entire country or entire world • typically composed of a combination of – terrestrial fixed satellite systems, coaxial cable, and fiber optical cable. • The public switched network and the Internet are examples of WANs.

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Networks Networks

• WAN • SAN – Storage area network • connects servers directly to devices to store data • moves storage resources off the common user network and reorganizes them into an independent, high-performance network. – So, each server is allowed to access shared storage. • This can involve Fibre-channel connection, similar to Ethernet, to handle high-performance disk storage for application.

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5 Networks Networks

• SAN • EPN – Enterprise Private Network • a computer network built to share computer resources among different sites – such as production sites, offices and shops of a business • Some of the advantages of an EPN: – The messages are secure because they are encrypted. – They are cost effective and scalable. – They help to centralize IT resources. – They enable business continuity.

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Networks Networks

• EPN • VPN – Virtual Private Network • an extended private network which spreads over the internet. • Users can send and receive data across shared or public networks. • It uses public wires – usually the internet to connect to a private network • usually a company’s private network. • The benefit of a secure VPN is its level of security to the connected systems, – whereas the other network infrastructure alone can not provide it.

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Networks Networks

• VPN • GAN – Global Area Network • a network composed of different interconnected networks that cover an unlimited geographical area. – The term is loosely synonymous with Internet, • which is considered a global area network. • BGAN – Broadband Global Area Network • a mobile communications system created to transmit broadband wireless voice and data communications almost anywhere on the earth's surface. – The system, developed by Immarsat, Inc., consists of a constellation of geostationary satellites working in conjunction with portable, lightweight, surface-based terminals about the size of a .

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6 Networks Networks

• WLAN • WLAN – Wireless Local Area Network • a wireless computer network that links two or more devices using a wireless distribution method within a limited area – such as a home, school, computer laboratory, or office building. • sometimes called a local area wireless network (LAWN) • The IEEE 802.11 group of standards specify the technologies for WLANs

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Networks Networks

• CAN • CAN – Controller Area Network • a serial bus network of microcontrollers that connects devices, sensors and actuators in a system or sub-system for real-time control applications. – Bosch originally developed the CAN in 1985 for in- vehicle networks • Lifts and escalators use embedded CAN networks Hospitals use the CANopen protocol to link lift devices, such as panels, controllers, doors, and light barriers, to each other and control them.

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Networks Communications Models

• IAN • In the traditional client-server model, a server – Internet Area Network provides data to one or more clients. • a concept for a communications network that • In contrast, in a peer-to-peer network, every computer acts as a server and client to other connects voice and data end-points within a computers on the network. cloud environment over IP, – As such, a particular computer might function as a – replacing an existing LAN, WAN or the public server one moment and as a client the next switched telephone network (PSTN). • The simplest type of computer network to • Cloud based IT & Communications interface construct in a small workgroup is a peer-to- peer network.

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7 Communications Models Communications Models

• The disadvantages of the peer-to-peer model – Uneven use of resources, • the workstations with the most relevant content are accessed more often than workstations with less frequently accessed content. – The result is decreased performance for computational tasks of the frequently accessed workstations. – Data management is more challenging. • Everyone in the workgroup must perform tasks such as archiving and updating antiviral utilities, for example.

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Communications Models Transmissions Technology

• A client-server model employs a central server to • Switched Communications provide programs and data files that can be – A fixed, continuous bi-directional connection is accessed by client workstations on the network. established between the message source and • An advantage of this model is that recipient. – the network running on the server provides for security, tiered access privileges, and no degradation of individual workstation performance • because files are accessed from the server. • In addition, the data and programs on the central server can be more easily and consistently archived, backed up, accessed, and shared.

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Transmissions Technology Protocols

• Packet Communications • Network protocols – formal standards and policies comprised of rules, procedures and formats that – Multiple, virtual communications channels are established by breaking up define communication between two or more devices over a network. messages into small packets and reassembling them at the destination – govern the end-to-end processes of timely, secure and managed data or network communication. • The key standards organizations that define or suggest network protocols: – the Open Systems Interconnection (OSI) group, – the Institute of Electrical and Electronics Engineers (IEEE), – the Consultative Committee on International Telegraphy and Telephony – International Telecommunications Union-Telecommunications Sector – the American National Standards Institute (ANSI), – the Exchange Carriers Standards Association (ECSA), – the Alliance for Telecommunications Industry Solutions (ATIS) • OSI, begun by the International Organization for Standardization in the late 1970s, defines high-level communications architectures, including the OSI Reference Model

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8 Protocols Key Network Protocols

• The OSI Reference Model • The most important IEEE standards in biomedical informatics: – OSI defines the communications process into seven different categories that Standard Description deal with communications and network access. IEEE 488 Computer to electronic instrument Layer Name Focus communications; also known as GPIB and 7 Application Semantics HPIB 6 Presentation Syntax IEEE-802 LAN and MAN standards 5 Session Dialog coordination IEEE-802.3 Ethernet; the most common LAN 4 Transport Reliable data transfer specification 3 Network Routing and relaying IEEE-802.3 10Base-T Ethernet over twisted pair cable 2 Data Link Technology-specific transfer IEEE-802.11 Wireless LANs 1 Physical Physical connections IEEE-802.11a 5 GHz, 54 Mbps wireless LAN; shorter range than 2.4 GHz systems, higher bandwidth, • The IEEE develops standards for the entire computing industry, including and more channels than WiFi wired and wireless networks IEEE-802.11b 2.4 GHz, 11 Mbps wireless LAN; the most – these standards define specific low-level functionality, such as operating common, most mature; limited channels, also frequency, bandwidth, message format, signal voltage, and connector style for computer networks. known as WiFi • For example, the IEEE-802.3 10BaseT standard defines Ethernet over ordinary twisted pair cable

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Key Network Protocols Bandwidth

Standard Description • There are three frequently used definitions of bandwidth in the IEEE-802.11e 2.4 GHz, 11 Mbps wireless LAN; enhanced context of : quality of service • In computer networks, IEEE-802.11g 2.4 GHz, 22 Mbps wireless LAN; higher- – bandwidth is data transfer rate, • the amount of data that can be carried from one point to another in a given time bandwidth version of 802.11b, limited channels period (usually a second). IEEE-802.11i 2.4 GHz, 11 Mbps wireless LAN; enhanced – Network bandwidth is usually expressed in bits per second (bps); security • modern networks typically have speeds measured in the millions of bits per second CCITT/ITU-T ISDN Digital communications over standard phone – (megabits per second (Mbps) lines • or billions of bits per second CCITT/ITU-T X.25 Switched packet communications – gigabits per second (Gbps) – Different applications require different bandwidths. ANSI FDDI High-speed (200 Mbps) fiber backbone LAN • An instant messaging conversation might take less than 1000 bits per second ECSA SONET Very high-speed (10 Gbps) optical network (bps); • A voice over IP (VoIP) conversation requires 56 kilobits per second (Kbps) to standard sound smooth and clear. DARPA TCP/IP The protocol of the Internet • Standard definition video (480p) works at 1 megabit per second (Mbps), but HD video (720p) wants around 4 Mbps, and HDX (1080p), more than 7 Mbps.

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Bandwidth Bandwidth

• In signal processing/communication, • Network Bandwidth – Bandwidth is the range of frequencies • Gigabit Ethernet, • the difference between the highest frequency signal component and Fast Ethernet, and the lowest frequency signal component Ethernet provide a • bandwidth is measured in hertz (cycles per second). tiered network • This is the original meaning of bandwidth, system that – although it is now used primarily in discussions about cellular networks and provides a the spectrum of frequencies that operators license from various governments compromise for use in mobile services. between system • In business, data throughput, cost, and – bandwidth is a synonym for capacity or ability. maintenance. – In this sense, it refers to having time or staffing available to tackle something

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9 Topology Topology

• The physical layout of a network • Bus topology: – a function of the practical constraints imposed by – A network topology in which all nodes (stations) are connected together by a single bus. • the environment, • the protocols that must be supported, • Mesh topology: • the cost of installation. – A network topology in which there are at least two nodes with two or more paths between them. • The most common protocols used with LANs, • Ring topology: Ethernet and token ring, assume a bus and ring – A network topology in which every has exactly two topology, respectively. branches connected to it. • The star topology is often used as a hub to connect • Star topology: several networks and in wireless networks, – A network topology in which nodes are connected to a central node, which rebroadcasts all transmissions received from – where multiple devices connect via radio frequency, it links any peripheral node to all peripheral nodes on the network, to a central wireless access point or wireless hub. including the originating node.

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Topology Topology

• Fully connected (Mesh) topology: – A network topology in which there is a direct path between any two nodes. – In a fully connected network with n nodes, there are n(n- 1)/2 direct paths. • Tree topology: – A network topology that resembles an interconnection of star networks in that individual peripheral nodes are required to transmit to and receive from one other node only, toward a central node, and are not required to act as or regenerators. • Hybrid topology: – A combination of any two or more network topologies.

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Hardware - Media Hardware - Media

• The most common media are • Media Characteristics – coaxial cable, – twisted pair wiring, – fiber optics, – the ether (for wireless networks) • Media Characteristics are reflected by – bandwidth, – cost, – security, – flexibility, – range • In this example, ether refers to wireless LAN signals

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10 Hardware - Media Hardware - Media

• Coaxial Cable • Fiber – the most popular media used in networks, – popular as a medium for LANs – glass fiber provides – inexpensive and provides the greatest flexibility in • the greatest bandwidth, installation • highest level of security, • greatest range, – the center conductor is shielded by a copper or aluminum • resistance to electrical noise. mesh or foil, – Although fiber provides a working range of up to several – provides a relatively secure connection and a high kilometers with standard electronics, • it's less flexible to install compared to copper cable. bandwidth. • For example, unlike twisted pair or coaxial cable, fiber can't be snaked through very tight turns because the glass fiber is more fragile than the – However, others • it's possible for someone with a sensitive receiver and antenna to – From a security perspective, fiber is the superior remotely pick up signals traveling through coaxial cable, amplify medium because there is no radio frequency signal that them, and decode the digital stream can be intercepted by a nearby receiver

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Hardware - Media Hardware - Media

• Twisted Pair • Power Line Cable – the wiring used in virtually every office and residence – a low-cost, low-bandwidth solution to networking. for telephone communications, – Although it may be suitable for exchanging text-only e-mails and other • is a comprise between cost, bandwidth, security, and small files, the limitations of the medium prevent it from being a serious availability. network medium for biomedical informatics applications. – more affordable than coaxial cable or fiber, – It may be a viable as part of a redundant backup network system. • but the bandwidth isn't as great, and security is a much • Ether greater concern. – provides the greatest flexibility, – When used with radio frequency network signals, • but also presents the greatest security risk. – Typical internal installations for wireless LANs are limited to the same • twisted pair cables don't perfectly cancel out the signals floor in a building. traversing the two wires, but act as antennas. – However, within that space, users may have complete mobility with • As a result, not only are signals in the cable more readily or desktop workstations that are frequently moved. intercepted, but the twisted pair cable is more susceptible to electrical noise in the environment. – Optical LANs, based on infrared (IR) links are line-of-sight only, and are limited to a single work area.

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Hardware - Media Hardware - Media

• Radio frequency communications are also commonly used • The type of media used for Internet access between buildings, in the form of links. depends • These links tend to be line-of-sight and limited to perhaps – primarily on the types of service available, ~50 km, depending on terrain and buildings that may – secondarily on the bandwidth, security, and cost interfere with line-of-sight communications. constraints. • Unlike the radio frequency technology used with LANs, • The choice of media that can be used to support the bandwidth of these links is on the same order as an internal LAN is more a function of coaxial cable. – cost, • Similarly, radio frequency satellite links that extend – bandwidth requirements, thousands of kms support high-bandwidth transmission – security, rates comparable to that provided by coaxial cable and – ease of installation, fiber media. – type of existing wiring, if any.

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11 Network Electronics Network Electronics

• The media running from office to office and across – Blocking signals from certain paths to the country become a useful communications minimize interference in those paths channel with the addition of electronics – Routing signals down the quickest or least- – capable of sending and receiving signals through the expensive route from source to destination media. – Translating signals originally designed to work • These electronics serve a variety of functions: with one protocol so that they are compatible – Generating signals destined for a recipient with networks designed to support other somewhere in the network protocols – Coordinating signals through media in order to – Connecting different networks minimize interference – Amplifying and conditioning signals so that they – Monitoring the status of the network, including can continue error-free to their destination the functioning of network electronics and the amount of data on segments of the network

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Network Electronics Network Electronics

• Several of the network devices Device Application Sends data transmissions only to the Device Application portion of a network meant to receive Bridge Connects multiple network segments and forwards data them between them Satellite Transmits signals from a server in orbit Content Filter Prevents access of restricted external Web content Server Supplies files and applications to clients Prevents unauthorized users from accessing the Selects network paths at high speeds Gateway Links two networks that use different protocols UPS Provides uninterruptible power for Hub Provides a central connection point for a network network electronics, especially servers configured in a star topology Wireless Hub Provides mobile, cable-free access to Modem Connects a workstation or LAN to an outside servers, shared resources, and the Internet workstation or network, such as the Internet from anywhere within range of the hub Monitor Monitors activity on the network by node and by Wireless Modem Allows workstations and laptops to communicate with a wireless hub (access point)

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Network Electronics Contents

• Network Hardware • Networks are sometimes defined by the nature of the content they carry. – For example, • Some networks capable of sustained high-bandwidth connections are dedicated to video and other , whereas others are limited to text. • Networks may also be relegated to or equipment communications. – The former is especially prominent in , in the form of storage area networks. • These networks, typically based on fiber optics, are maintained for highspeed communications between disk arrays and computers involved in sequencing and other applications that require almost constant access to data stored on high-speed hard drives. • The physical architecture shown here may support a markedly different logical architecture. 71 72

12 Security Security

• is an increasingly important • Although it may be practically impossible to factor in informatics maintain security from professional industrial spies, – because of the central role that online , – a variety of steps can be taken to minimize the threat applications, and groupware such as e-mail play in posed by modestly computer-savvy activists and the the day-to-day operation. most common non-directed security threats. • Opening an intranet to the outside world • These steps include through username and password protected – using antiviral utilities, restricted access may be the basis for – controlling access through the use of advanced user- authentication technologies, collaboration as well as a weak point in the – firewalls, security of the organization. – low-level encryption technologies.

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Security Security

• Antiviral Utilities • Authentication • The risk of virus infection can be minimized by • The most often used method of securing access installing virus-scanning software on servers to a network is to verify that users are who they and locally on workstations. say they are. • The downside to this often-unavoidable precaution is decreased performance of the • However, simple username and password computers running antiviral programs, as well protection at the firewall and server levels can as the maintenance of the virus-detection be defeated by someone software to insure that the latest virus – who either can guess or otherwise has access to the definitions are installed. username and password information.

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Security Security

• A more secure option is to use a synchronized, • Firewalls • stand-alone devices or programs running on a server that pseudorandom number generator for passwords. block unauthorized access to a network. – In this scheme, two identical pseudorandom number • Dedicated hardware firewalls are more secure than a generators, one running on a credit card–sized software-only solution, computer and one running on a secure server, generate – but are also considerably more expensive. • Firewalls are commonly used in conjunction with proxy identical number sequences that appear to be random to servers to mirror servers inside a firewall, an observer. – thereby intercepting requests and data originally intended for an • More sophisticated methods of user authentication internal server. • In this way, outside users can access copies of some subset involve biometrics, the automated recognition of of the data on the system without ever having direct access fingerprint, voice, retina, or facial features. to the data. – This practice provides an additional layer of security against hackers.

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13 Security Security

• Encryption • Encryption Standards • the process of making a message unintelligible to all but the intended recipient Standard Description AES Advanced Encryption Standard—Eventual replacement for • one of the primary means of ensuring the security of DES, based on 128-bit encryption. messages sent through the Internet and even in the same DES Data Encryption Standard—Used by the government, based building. on 64-bit encryption. IDEA International Data Encryption —Used by the • also one of the greatest concerns—and limitations—of banking industry, developed by the Swiss Federal Institute of network professionals. Technology, 128-bit encryption. PGP Pretty Good Privacy—Popular on the Internet, effective, free, • Although cryptography predates computers by several simple to use. millennia, no one has yet devised a system that can't be RSA Rivest-Shamir-Adelman System—Popular in business and defeated, given enough time and resources. government. – Every form of encryption has tradeoffs of security versus S-HTTP Secure Hypertext Transfer Protocol—For transmitting processing and management overhead, and different forms individual messages over the Internet. SSL Secure Sockets Layer—Developed by Netscape of encryption are used in different applications Communications Corp. for the Internet.

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Security Ownership

• Process • Networks are often characterized by the way they are • More important than the specific encryption algorithm funded. or user-authentication technology used is the process of • Private networks are owned and managed by private implementing a security strategy. corporations. – For example, the best firewall, , and user – For example, many of the major pharmaceutical authentication system is valueless if a researcher has a habit corporations have internal bioinformatics R&D groups that of losing his secure ID card. manage workflow and data with the help of privately owned – Similarly, a wireless hub capable of supporting the latest and highly secure networks. security standards is vulnerable to attack if the person who • These private networks may be completely isolated, configures the hub doesn't take the time to enable the connect to the Internet through a secure firewall, or security features. communicate with academic and commercial – Similarly, a researcher who leaves her username and collaborators through dedicated, secure lines. passwords on a Post-It Note stuck to her monitor provides a security hole for everyone from the janitorial staff to a • Private networks may also be open to researchers and visitor who happens to walk past her office. other companies—for a fee.

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Ownership Implementation

• Public networks such as the Internet and the public • The major steps in the implementation process: telephone network are at least partially funded by public coffers. • Create a Requirements Specification. • They are also freely open to anyone who is capable of – This document includes a high-level description of the paying for their services. tasks to be supported by the network, • Cooperative networks are supported and managed by their users. • such as routing sequencing data from sequencing machines to analysis workstations and data warehouses, – One of the best known cooperative networks was BITNET (Because It's Time Network), started by universities in the – as well as the desired response times and storage capacities. early 1980s. • For example, the requirements specification document may – Before it was replaced by NSFNET (National Science stipulate the need to support 35 workstations, provide access Foundation Network) in the early 1990s, it connected about to storage in excess of 1 terabyte with an access time of less 3,000 mainframe computers at universities in the U.S., than 50 milliseconds, with tiered password protection, and Canada, South America, Europe, Asia, and Australia. secure, high-speed access to the Internet.

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14 Implementation Implementation

• Create a Functional Specifications Document • Select Software. – that defines, in detail, how the high-level needs outlined in the requirements specification will be met. – This step of the implementation process involves • This document quantifies many of the qualitative terms in the selecting the network operating system, as well as requirements specification to the degree that anyone competent in information sciences can determine exactly database publishing software and tools such as what equipment, personnel, and costs will be associated with PHP, XML, CGI, Java, or JavaScript editors and the project. runtime systems. • Select Hardware. – Assuming the functional specifications document is • Select Utility. complete, the next step is selecting network, – Software and hardware utilities, such as network workstation electronics, and media. • Often the functional specifications document is authored with monitors and antiviral utilities, should be defined particular hardware and software in mind, which further during the design process, not as an afterthought. simplifies the selection process.

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Implementation Management

• Select Internet Access Service. • After a network is established, it must be managed to realize its full potential. – Most larger institutions have high-speed Internet • Network management issues include access available throughout their offices. – making provision for disaster recovery, • However, bandwidth requirements may necessitate – load balancing, alternate Internet services, – bandwidth management, – such as supplementing a corporate-wide cable modem service – maintaining network security. with a high-speed dedicated line, satellite link, or high-speed microwave link. • For example, disaster recovery plans and support for inevitable network electronics and media failure should consider – fire, electrical disturbances, power outages, or intentional destruction.

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Management

• Part of disaster recovery planning includes – securing redundant systems, • such as running extra cables when installing a wired network – installing a bank of 56K dial-up available for Internet access in the event that the high-speed Internet connection fails. • Perhaps the greatest management challenge is maintaining adequate security. – This task entails monitoring the Internet on a daily basis • to check for word of new viruses or security holes in the operating system, and installing the appropriate software patches and utilities to address the new threats.

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15 Grammar revision Grammar revision

• Comprise, can be used with the parts that make • Comparison and contrast up something as the subject: • Example: Comparison of digital and conventional cameras – {Oil and coal comprise 70% of the nation’s FEATURE DIGITAL CONVENTIONAL lens   exports.} viewfinder   • Compose requires chemical x  processing • Compose of is even more formal than consist film x  transfer images  x of and comprise. directly to PC can delete  x • Compose of is only used in the passive voice: unsatisfactory images – {Muscle is composed of different types of protein.} • Note how we can compare and contrast these types of cameras

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Grammar revision Grammar revision

• Comparing features which are similar: – {With a you can transfer images – {Both cameras have lenses.} directly to a PC but with a conventional camera you need to use a scanner.} – {Like the conventional camera, the digital camera has a viewfinder.} – {With digital cameras you can delete unsatisfactory images; however with conventional cameras you • Contrasting features which are different: cannot.} – {The conventional camera requires chemical processing whereas the digital camera does not.} – {The conventional camera uses film unlike the digital camera.}

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